The present invention relates generally to transfer switches and, more particularly, to a combination transfer switch and circuit breaker.
Transfer switches are designed to selectively electrically connect a load to one of two power supplies. Representatively, a transfer switch may be used to connect an electrical load, to either a main power supply, such as a utility power supply, or an auxiliary power supply, such as an electric generator. In most conventional applications, the transfer switch will have a single-pole, double-throw switch for each branch circuit of a load center or main panel that is to be powered by the auxiliary power supply during interruption of the main power supply. Each switch is operable in either a LINE position, which is its normal operating position when the main power supply is supplying power to the branch circuit, or a GEN or AUX position in which the auxiliary power supply is used to supply power to the branch circuit. Conventional transfer switches have been designed to have separate branch circuit switches and circuit breakers for each branch circuit to be fed when connected to receive power from the auxiliary power supply.
Combination switch and circuit breakers have been designed to overcome some of the drawbacks associated with separate switch and circuit breaker arrangements. Specifically, single-pole, single-throw combination switch and circuit breakers have been developed to provide switching and circuit breaking functionality in a single device. While reasonably effective, these combination switch and circuit breakers are constructed to have only an ON position or an OFF position. That is, current flow is only permitted between a single power supply and a load (branch circuit) when the combination switch and circuit breaker is in the ON position. When in the OFF position, current is prevented from flowing from the power supply to the load. Because the combined device provides some overcurrent protection, it may automatically move to the OFF position if an excessive current condition is detected while in the ON position. While such combination devices have reduced the size and complexity of transfer switches, these combination devices only permit connection to a single power supply, typically the auxiliary power supply. Therefore, to connect the branch circuit to the main power supply, a switch device must be used that is separate from the switch device used to connect the branch circuit to the auxiliary power supply.